IT'S a tedious job, but someone has to do it. Or many someones, in this case.

For the past 21 years the task of sorting the loose change collected in UNICEF charity envelopes on Qantas flights has come down to a small team of volunteers.

From an ordinary office at the airline's Sydney headquarters, they sit and sort 140 currencies donated on domestic and international flights into milk cartons. The cartons, which line an entire wall, are divided into rows of countries in alphabetical order.

As well as thongs, golf ball markers and hearing aids, volunteers have found casino chips, unclaimed lottery tickets, watches, engagement and wedding rings over the years.

"We have had men's and women's rings in the same envelope," senior co-ordinator Peter Nolan says.

"It might have been an in-flight divorce or something."

There have also been a few big cheques, including one for $25,000 from a well-known Australian businessman.

"The same guy wrote a cheque for $10,000 a few years later," Nolan says.

A "big notes" competition was started by staff in 1994, and every time someone finds a note worth $100 - or a large cheque - they get a centimetre-long line drawn beside their name on a whiteboard on the wall.

Whoever has the longest line at the end of the year receives a gift.

Over the past two decades, UNICEF's Change for Good program has raised $25 million. The money goes towards vaccinating babies in developing countries, providing malaria-preventing mosquito nets, HIV education campaigns and supporting orphans.

It helped provide emergency relief after the 2004 Boxing Day tsunami and the Haiti earthquake.

From last month, Qantas frequent flyers were also able to use their points to donate to the program.

Nolan, 58, is a former flight attendant and cabin crew manager who took on his role, a full-time, paid position, 15 years ago. He leads a team of 12 regular volunteers, all retired Qantas staff, and a different group works each day.

"I was a bit sick of travelling to be honest," Nolan says. "It was what I did for a living. I like working with these guys; they seem to enjoy it."

To make the sorting easier, the bags of coins that arrive from around the world are divided into where the flight has come from.

"A UK bag is more likely to have UK currency," Nolan says.

They are then weighed, packed in milk containers and sent to a company called Coin Co in Brisbane to be counted properly in machines.

The volunteers know that a bag of US quarters is worth roughly $US90.

Between 300kg and 400kg of coins are sent to Brisbane each week.

A volunteer named David Paterson, who still works there at age 78, started the milk carton system.

"He came up with the idea and it's worked so well we haven't bothered looking for another one," Nolan says.

Coin Co became involved in the project about eight years ago when the chief executive of the company sat next to someone from UNICEF and they got chatting about what happened with the money. Prior to that coins were sent to London and Los Angeles to be counted.

Over the past few years, Nolan has done a few trips to northern Thailand and Cambodia to visit orphanages and see where the money goes.

"It's a really feel-good job and that's why I'm still here," he says.

"The kids are so cute but they're very, very poor. They don't have proper food or sanitation and their parents often don't have any work.

"I'd been doing it a long time and I'd never seen where the money had gone and that gave me a kick along in terms of my enthusiasm.

"When you're there and you see where the money is going it gives you a boost."